This invention relates generally to fluid nozzles, and more particularly to nozzles for use with fire fighting equipment of the type used by professional firefighters.
A common method of extinguishing fires is, of course, to apply a large quantity of water to the burning material or structure. The water is applied by projecting a stream from a nozzle and a hose connected to a water supply, and numerous nozzle designs have been used and described in prior art patents. One objective of nozzle designers is to regulate the water pressure at the nozzle outlet to achieve a substantially constant outlet pressure despite variations in the supply pressure. The commonly accepted outlet pressure is 100 psi.
U.S. Patents that describe automatic outlet pressure regulating mechanisms are, for example, No. 3,539,112; No. 3,684,192; No. 3,863,844; No. 3,948,285; and No. 4,252,278.
Generally, the regulating mechanisms include a spring-loaded baffle at the nozzle outlet. If the supply pressure increases, for example, the water pressure moves the baffle to increase the outlet flow area and thereby maintain the pressure substantially at the preset value. The opposite action occurs, of course, if the supply pressure drops.
Nozzles with pressure regulating mechanisms have operated satisfactorily under normal operating conditions. In an emergency situation, however, the supply pressure may drop to an abnormally low value. In this case, there is a danger that the water pressure on the baffle is not sufficient to hold it substantially open, and the outlet flow area may decrease to the point where an inadequate amount of water flows from the nozzle.
U.S. Pat. No. 4,252,278 shows a nozzle including a baffle 48 mounted on a post 50, and a compression spring 52 which urges the baffle 48 toward an insert 46. When using this nozzle, the baffle 48 would tend to move toward the insert 48 and reduce the flow area of the throat 44 if the supply pressure were to drop. This patent states that the nozzleman may adjust the position of the baffle 48 on the post 50. The baffle may be moved away from the insert 46 to flush out entrapped debris or when an inadequate supply pressure exists. Thereafter the nozzleman is supposed to return the baffle to its normal position. A shortcoming of the foregoing arrangement, when the baffle is moved when a low pressure condition exists, is that the flow area, or orifice, will likely be either too large or too small. While in theory the baffle 48 may be adjusted to an appropriate position, in practice a firefighter may not have sufficient presence of mind to do this in an emergency situation as when fighting a fire and the water supply pressure drops.
It is therefore a general object of the present invention to provide an improved nozzle having advantageous features.